Regulation of apoptosis is impaired in atrophic gastritis associated with gastric cancer

BACKGROUND

Gastric premalignant conditions, atrophic gastritis (AG) and intestinal metaplasia (IM) are characterized by an increase of proliferation and a reduction of apoptosis in epithelial cells. The epithelial cell kinetics in AG and IM in gastric mucosa adjacent to gastric cancer is still unclear. The aim of this study was to evaluate the epithelial cell turnover and expression of proliferation and apoptosis-related genes in gastric cancer (GC) and adjacent mucosa with atrophic gastritis or intestinal metaplasia (AG/IM GC+), as well as in atrophic gastritis or intestinal metaplasia mucosa of patients without GC (AG/IM GC-) and in control biopsy samples of non-transformed gastric mucosa (Control).

METHODS

We selected 58 patients (M: F = 34:24; age range 20-84 years, median 61.06 years) with 4 well defined histological conditions: 20 controls with histological finding of non-transformed gastric mucosa, 20 patients with AG or IM (AG/IM GC-), and 18 patients with intestinal type gastric adenocarcinoma (GC) and AG or IM in the adjacent mucosa (3 cm from the macroscopic tumour margin, AG/IM GC+). We performed an immunohistochemical staining of Ki67 and TUNEL and quantitative RT-PCR to determine the expression of PCNA and Bax/Bcl-2.

RESULTS

The immunohistochemical expression of Ki67 and TUNEL in AG/IM GC- was significantly increased compared to not transformed gastric mucosa (p < 0.0001) but not compared to AG/IM in gastric mucosa adjacent to GC. Levels of Bcl-2 were reduced in GC and AG/IM GC- compared to controls as well as in AG/IM GC- compared to AG/IM in mucosa adjacent to GC+ (p < 0.05). Proliferation and apoptosis markers did not correlate with H.pylori status in our study population.

CONCLUSIONS

In AG/IM associated with GC, no significant changes in the epithelial cell turnover were detected. Decreased Bcl-2 gene expression signified atrophic gastritis and IM in presence of cancer, as well as intestinal type gastric adenocarcinoma.

Clinical symptom tool that raises the index of suspicion for eosinophilic oesophagitis in adults and drives earlier biopsy for definitive diagnosis

BACKGROUND

Eosinophilic oesophagitis (EoE) and gastro-oesophageal reflux disease (GERD) present with overlapping symptomatology and it is challenging to distinguish EoE from GERD clinically before endoscopy.

AIM

To investigate the prognostic value of a set of clinical symptoms and laboratory values in patients with EoE and GERD.

METHODS

In this prospective, single-centre, observational study, we compared clinical and laboratory data from 202 patients with EoE or GERD (10 relevant characteristics). Those characteristics showing potential significance in a univariate analysis were then included in a multivariate analysis.

RESULTS

The set of 10 characteristics (10-marker set) was able to distinguish between EoE and GERD with good reliability (correct assignment, i.e. agreement with subsequent EGD, of 94.4%). Reduction of the set to the six statistically and clinically most relevant markers continued to give good reliability (88.9%), and further stepwise reduction led to four-marker sets comprising history of atopy, history of food impaction, proton pump inhibitor refractory symptoms and either immunoglobulin E or peripheral eosinophilia, with correct assignment rates of 91.3% and 85.1% respectively.

CONCLUSIONS

We have developed a simple and easily applicable clinical/laboratory marker set that helps to distinguish EoE from GERD earlier in the treatment course, thus guiding the endoscopist to perform biopsies from the oesophagus to ensure the diagnosis. The application of the scoring system is expected to diagnose EoE earlier and avoiding delay of adequate treatment.

Leukotriene receptor expression in esophageal squamous cell cancer and non-transformed esophageal epithelium: a matched case control study

BACKGROUND

Leukotriene B4 (LTB4R and LTB4R2) and cysteinyl leukotriene receptors (CYSLTR1 and CYSLTR2) contribute to malignant cell transformation. We aimed to investigate the expression of LTB4R, LTB4R2, CYSLTR1 and CYSLTR2 in esophageal squamous cell carcinoma and adjacent non-transformed squamous epithelium of the esophagus, as well as in control biopsy samples from esophageal squamous epithelium of patients with functional dyspepsia.

METHODS

Expression of LTB4R, LTB4R2, CYSLTR1 and CYSLTR2 was analyzed by immunohistochemistry (IHC) and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in biopsy samples of 19 patients with esophageal squamous cell cancer and 9 sex- and age-matched patients with functional dyspepsia.

RESULTS

LTB4R, LTB4R2, CYSLTR1 and CYSLTR2 were expressed in all biopsy samples. Major findings were: 1) protein levels of all leukotriene receptors were significantly increased in esophageal squamous cell cancer compared to control mucosa (p < 0.05); 2) CYSLTR1 and CYSLTR2 gene expression was decreased in cancer tissue compared to control at 0.26-fold and 0.23-fold respectively; 3) an up-regulation of LTB4R (mRNA and protein expression) and a down-regulation of CYSLTR2 (mRNA expression) in non-transformed epithelium of cancer patients compared to control (p < 0.05) was observed.

CONCLUSIONS

The expression of leukotriene receptors was deregulated in esophageal squamous cell cancer. Up-regulation of LTB4R and down-regulation of CYSLTR2 gene expression may occur already in normal squamous esophageal epithelium of patients with esophageal cancer suggesting a potential role of these receptors in early steps of esophageal carcinogenesis. Larger studies are warranted to confirm these observations.

Helicobacter pylori infection is associated with a reduced risk of developing eosinophilic oesophagitis

BACKGROUND

Eosinophilic oesophagitis (EoE) represents a chronic immune-antigen-mediated allergic disease of the oesophagus of still unknown aetiology. Environmental exposure has been postulated to play a pathogenetic role. Helicobacter pylori (H. pylori) infection has been inversely associated with allergic diseases including atopic dermatitis, asthma and allergic rhinitis and H. pylori may play a protective role in these conditions. Little is known about the relationship between EoE and H. pylori.

AIM

To investigate in a case-control study whether H. pylori infection is associated with a reduced risk of developing EoE.

METHODS

H. pylori infection was evaluated by serology in 58 [11(19%) female, 47 (81%) male, median age: 36.5 years, range 20-72 years] patients with a clinical and histologically proven diagnosis of EoE and 116 age and sex-matched controls (1 case: 2 controls). Antibodies against H. pylori were identified by enzyme-linked immunosorbent assay. Patients with H. pylori-specific IgG ≥ 30 enzyme immunounits were classified as H. pylori-positive.

RESULTS

3/58 (5.2%) patients with EoE had serological evidence of H. pylori infection (EoE - H. pylori current infection) and 5/58 (8.6%) reported prior eradication therapy for H. pylori infection (EoE - H. pylori former infection). The control group demonstrated significantly higher seroprevalence of H. pylori (37.9%, P < 0.0001) when compared to patients with EoE. EoE was inversely associated with H. pylori infection [odds ratio (OR) 0.24, 95% confidence interval (CI) 0.11-0.50].

CONCLUSION

Helicobacter pylori infection is inversely associated with EoE. Our results may contribute to further understanding the pathogenesis and evolving aetiology of EoE.

Histomorphological differentiation of non-erosive reflux disease and functional heartburn in patients with PPI-refractory heartburn

BACKGROUND

Proton pump inhibitor (PPI)-refractory heartburn may be due to persistent gastro-oesophageal reflux, oesophageal hypersensitivity or functional heartburn (FH). The differentiation between non-erosive reflux disease (NERD) and FH may be very difficult. However, this differentiation is important for appropriate therapeutic management. Dilated intercellular spaces (DIS), papillary elongation (PE) and basal cell hyperplasia (BCH) can be all assessed by light microscopy. Whether these mucosal abnormalities allow the differentiation of NERD from FH in PPI-refractory patients is uncertain.

AIM

To assess histopathological findings by light microscopy in patients with refractory heartburn to differentiate NERD from FH.

METHODS

Sixty-two patients with PPI-refractory symptoms underwent EGD and MII-pH after pausing PPI medication for 2 weeks before investigation. Twenty-five subjects without upper gastrointestinal symptoms were included as controls. Symptom assessment was based on the reflux disease questionnaire (RDQ). Biopsies were taken 3-5 cm above the gastro-oesophageal junction. DIS, PE, BCH and infiltration of immune cells were evaluated and a sum score was calculated.

RESULTS

Based on endoscopy and MII-pH, GERD was diagnosed in 43 patients (NERD: 20; ERD: 23) and FH in 19 patients. There was no difference in symptoms between the groups. Each individual histopathological item was different between the groups (P < 0.0001). Between NERD and FH, the most significant difference was found for DIS and the histopathological sum score (P < 0.001).

CONCLUSIONS

These findings suggest that oesophageal biopsies are useful to differentiate NERD from FH. Increased DIS and a histological sum score are the most significant histopathological abnormalities in NERD as compared with FH.

[What Must the (Abdominal) Surgeon Know about Experimental Medicine (?) - Translational Research in General (Abdominal) Surgery(Viszeral-)Chirurg & experimentelle Medizin]

Experimental medicine has evolved tremendously in the last few years. In particular, the introduction of novel techniques, in-vitro models, knock-out/transgenic animals and high-through put analytical methodologies have resulted in a deeper understanding of cellular pathophysiology and diseases. The daily clinical management has benefited by the introduction of biomarkers and targeted therapies. This development has been accompanied by increasing specialisation across all fields of research and medicine. Therefore, clinical-translational research requires a team of competent partners nowadays. The visceral surgeon can contribute significantly to these projects. The present review highlights several aspects of translational research and put chances and potential pitfalls into perspective in context with the work of the visceral surgeon.

Helicobacter pylori related and non-related lesions in the stomach

Gastric lesions may arise in gastric mucosa of patients with gastritis or gastropathies due to different etiopathogenic factors. As most lesions of the stomach result from a chronic infection of gastric mucosa with Helicobacter pylori (H. pylori), a possible classification of gastric lesions based on etiology may distinguish H. pylori-related lesions from those arising in a gastric mucosa not colonized from the bacterium. The repertoire of lesions one may find in the stomach is limited and different pathologies may present with a similar macroscopic aspect. Clinically relevant lesions of the stomach that are or are not associated with H. pylori infection include gastric ulcer, gastric atrophy, gastric neoplasia, and metastasis from other cancers. The detection or exclusion of an H. pylori infection in patients with gastric lesions has important consequences for the clinical management. In the present review we focus on H. pylori-related and non-related peptic lesions in the stomach.

IL-17A and IL-17F gene expression is strongly induced in the mucosa of H. pylori-infected subjects from Kenya and Germany

Helicobacter pylori infection is the major cause of gastritis. Immunologically, H. pylori gastritis is associated with an infiltration of immune cells into gastric mucosa and the upregulation of various cytokines. Here, we analysed the gene expression of IL-1- and IL-17-related cytokines in regard to H. pylori infection in 85 German and 51 Kenyan patients with reflux-related or dyspeptic symptoms, respectively. Degree of gastritis and density of colonization were assessed histologically in accordance with the updated Sydney classification. Gene expression levels of cytokines IL-1β, IL-8, IL-18, IL-33, IL-17A, IL-17F and IL-23 as well as IL-23R were analysed by real-time RT-PCR. In both populations, H. pylori-infected individuals had significant higher inflammatory scores for activity and chronicity than H. pylori-negative subjects (P values between 0.006 and <0.0001). IL-8 mRNA was induced up to 6-fold in H. pylori-infected patients (P < 0.05), while the expression levels of IL-1β, IL-18, IL-23, IL-33 and IL-23R did not differ with respect to the H. pylori status in both groups. Most strikingly, a significant induction of both IL-17A and IL-17F was noted in H. pylori-infected individuals of both ethnic groups. Almost all IL-17F-positive samples revealed co-expression of IL-17A (40/42, 95.2%). Analysing IL-17A and IL-17F transcript levels of these 40 'double-positive' samples, a highly significant positive correlation between both genes was identified (P < 0.001). Taken together, H. pylori infection leads to a strong upregulation of both IL-17A and IL-17F in the gastric mucosa suggesting a regulatory link between both genes.

Host polymorphisms of immune regulatory genes as risk factors for gastric cancer

The infection of the stomach with the gram-negative bacterium Helicobacter pylori is the main risk factor for the development of gastric cancer (GC). This led to the classification of this germ as "definite carcinogen" by the World Health Organization in 1994. The current model of gastric carcinogenesis is based on the interaction of multiple risk factors including virulence factors of the bacterium (e.g. CagA, VacA), environmental factors (diet, smoking) and host factors (gene polymorphisms). The complex interplay among these factors determines the clinical outcome of the infection leading to at least one of three major diseases in 1 out of 7 infected persons, namely ulcer disease, GC and "mucosa-associated lymphoid tissue" lymphoma in 15 %, 1% and 0.1% of all persons infected with H. pylori, respectively. Recently, an increasing number of genomic polymorphisms, mostly single nucleotide polymorphisms have been identified as risk factors for gastric cancer. Among them are genes encoding for cytokines, pattern recognition receptors, cell cycle-regulators, proteases, HLA-molecules, and enzymes for detoxification. In the last years it has become clear that an uniform "genomic risk pattern" for all GC patients does not exist. Most of these host factors are restricted either to the histological type (intestinal vs. diffuse), ethnical background (particularly Caucasian vs. Asian) and tumor localization (non-cardia vs. cardia cancer). Here, we review the current knowledge about the role of host factors for the gastric carcinogenesis focusing on immune-regulatory genes, in particular on the cytokine interleukin-1beta.

Low-dose aspirin reduces the gene expression of gastrokine-1 in the antral mucosa of healthy subjects

BACKGROUND

Gastrokine 1 (GKN1), one of the most abundant transcripts in normal stomach, is down-regulated by Helicobacter pylori infection. Aspirin (ASA), which is often used for secondary prevention of cardiovascular events, can damage gastric-duodenal mucosa within 1 or 2 h of ingestion.

AIM

To study the gastric mucosal expression of GKN1 during acute low-dose ASA consumption.

METHODS

Ten H. pylori-negative human volunteers took 100 mg ASA per day for 1 week, and underwent multiple upper GI endoscopies. GKN1 expression was analysed in antral and corpus mucosa by quantitative reverse-transcriptase polymerase chain reaction, western blot and immunohistochemistry (IHC). Gastric mucosal damage was detected endoscopically and histologically.

RESULTS

Gastrokine 1 was similarly expressed in both antral and corpus mucosa. The use of low-dose ASA led to a significant decrease (3.07 a.u. vs. 0.23 a.u., P < 0.001) in antrum at day 7, while GKN1 transcript levels in corpus mucosa were slightly elevated (twofold, P < 0.005). Western blot and IHC confirmed these changes at the protein level. Furthermore, IHC revealed a vesicular staining pattern in the cytoplasm for GKN1 that was confirmed by transfected human gastric adenocarcinoma cell line expressing GKN1.

CONCLUSION

Our data demonstrated that low-dose ASA downregulates GKN1 expression specifically in antral mucosa.

Palliative treatment of unresectable pancreatico-biliary cancer by either gemcitabine or octreotide/imatinib: Impact on biomarkers of angiogenesis

15101

Background: Gemcitabine represents standard Tx for unresectable cancers of the pancreas / distal biliary tract. Recent interest has focused on antiangiogenic properties in a mouse model of pancreatic cancer (JCI 2003); either VEGF or PDGF inhibition alone were less effective than the combination of both in terms of angiogenesis. In humans, imatinib (targeting PDGF) alone has been shown to be equivalent to gemcitabine in terms of survival (Cancer Lett. 2006;233:328–37), while most trials for octreotide (targeting IGF-1, VEGF) were disappointing. In HCC pts. we recently evaluated the impact of biomarkers on disease progression and survival (Cancer Res Clin Oncol 2006; 132:699–708). Methods: To investigate in a phase I/II trial the feasability of a combination (group I, n=11) of octreotide (30 mg im every 4 weeks, targeting VEGF-A) plus imatinib (400 mg po daily, targeting PDGF-B) vs gemcitable (group II, n=11, 1000mg/m2 weekly for 7/8 wks, then for 3/4 wks). Pts had either unresectable pancreatic cancer (n=18) or ampullary cancer (n=4). Primary outcome measure were changes in biomarkers (VEGF-A, PDGF-BB, soluble E-selectin, Ca19–9, CEA). Secondary outcome measures were TTP and OS. Results: 19/22 pts. had biomarker data available within the first 12 wks, changes over time are shwon in table . Median TTP was 109 vs 166 days (p<0.05) and median OS was 163 vs 325 days (p=NS) for group I vs II. Baseline Ca19–9 levels correlated with prognosis independent of Tx (p=0.05). In group I, high levels of PDGF-BB and VEGF-A levels at wk 12 but in group II, low levels of VEGF-A and s-E-selectin correlated with a better OS (p<0.05 each). TTP showed no correlations with biomarkers. Conclusions: The combination of octreotide plus imatinib is clinically less effective compared to gemcitabine. Although the absolute changes of angiogenesis markers are comparable between groups, chemotherapy compared to targeted therapy has a different impact on these in terms of survival.

[Table: see text]

No significant financial relationships to disclose.

Octreotide Alone or in Combination with Rofecoxib as Palliative Treatment for Advanced Hepatocellular Cancer

BACKGROUND

Median survival for advanced hepatocellular carcinoma (HCC) is around 3 months. Previous octreotide-based treatment studies revealed conflicting results.

AIMS AND METHODS

To determine whether palliative treatment for HCC is beneficial in terms of survival and quality of life (primary outcome measures). Patients were prospectively randomised to receive open-label octreotide 30 mg monthly alone (n = 39) or in combination with rofecoxib (up to 50 mg bid daily, n = 32) for a minimum of six months, or until death occurred.

RESULTS

Median overall survival (154 days) and time to progression (94 days) were similar for both treatments and within the range of published trials for octreotide, while adding rofecoxib to octreotide did not alter overall survival (149 vs. 155 days, p = 0.849). Treatment-associated clinical benefit was seen in 16/71 patients (3 patients with partial remissions and 13 with stable disease). Delay in tumor progression was associated with prolonged median survival (p < 0.0001) and a better quality of life (p < 0.05). Moreover, survival outcome was associated with a CLIP score < 3, extent of portal vein infiltration, well-differentiated tumor histology, prothrombin time, alkaline phosphatase, bilirubin, serum ferritin, and gamma-glutamyltransferase (p < 0.01 each).

DISCUSSION

Rofecoxib added to octreotide treatment did not improve survival over octreotide treatment alone. Octreotide treatment, although without major side effects, cannot be recommended in general as monotherapy, unless the few patients responding can better be characterised. There may still be a role for combining octreotide with other emerging targeted therapies because of potentially synergistic modes of action.

Low prevalence of Helicobacteraceae in gall-stone disease and gall-bladder carcinoma in the German population

Colonisation of the hepatobiliary system with bile-resistant Helicobacter spp. has been proposed as a novel risk-factor in the pathogenesis of gall-bladder carcinoma (GBC). There are reports that biliary Helicobacter colonisation is frequent in countries with a high incidence of gall-bladder carcinoma. However, the prevalence of Helicobacteraceae in the gall-bladders of patients with GBC in Germany, a region with a low incidence of GBC, is unknown. Therefore, gall-bladder tissue from 99 patients who had undergone cholecystectomy was tested, including 57 cases of gall-stone disease (GSD), 20 cases of GBC, and 22 control patients. The presence of Helicobacter spp. was investigated by culture, immunohistochemistry and a group-specific PCR targeting the 16S rRNA gene of all currently known Helicobacteraceae. Of the 99 cases investigated, only one patient with GSD was PCR-positive for Helicobacteraceae. For this individual, sequence analysis of the 16S rRNA gene showed that it had homology closest to the 16S rRNA sequence of Helicobacter ganmani. Helicobacteraceae were not detected by culture or immunohistochemistry. The low prevalence of Helicobacteraceae in the gall-bladders investigated suggests that Helicobacteraceae do not play a predominant role in the pathogenesis of GSD and GBC in the German population. The low prevalence could be a possible explanation for a relatively low incidence of GBC in the German population, despite the fact that GSD, the major risk-factor for GBC, is highly prevalent.

Impact of biomarkers on disease survival and progression in patients treated with octreotide for advanced hepatocellular carcinoma

BACKGROUND

Current determination of prognosis for advanced hepatocellular carcinoma (HCC) is mainly based on clinical assessment. We aimed to determine the impact of biomarkers as predictive factors for HCC progression and survival during octreotide-based treatments.

PATIENTS AND METHODS

We included patients who had been prospectively randomised to receive either octreotide (30 mg) alone monthly (n = 39) or in combination with rofecoxib (up to 50 mg bid daily, n = 32) for a minimum of 6 months, or until death occurred.

RESULTS

Overall median survival (154 days) and median time to progression (94 days) were not different for both treatments and the biomarkers investigated (VEGF-A, IGF-1, PGE-2, ET-A) were similarly distributed amongst treatment groups. Combined univariate group analysis revealed that survival was decreased for an uptake ratio of > 2 on initial octreoscan (P = 0.05); baseline serum VEGF-A and IGF-1 were further significantly associated with survival. On multivariate analysis, uncorrected serum VEGF-A appeared to be the most significant predictor for tumor progression and survival.

CONCLUSIONS

Biomarkers, in addition to established tumor markers, are independent predictors of tumor progression and survival in patients with advanced HCC treated with octreotide. Furthermore, the involvement of VEGF-A implies the inhibition of angiogenesis as a potential mechanism of action for this drug.

Imatinib for hepatocellular cancer (HCC)—Focus on PK/PD modelling and liver function

13088

Background: Imatinib represents standard medical care for treatment of gastrointestinal stroma tumors (GIST) and chronic myeloic leucemia (CML). Indications for other malignancies are evolving, especially in the context of antiangiogenesis, mediated by the inhibition of platelet-derived growth factor (PDGF). Liver metastasis occurs often in GIST patients, usually not affecting liver function. No reliable data about imatinib metabolisation under conditions of true hepatic impairment are available. Methods: Phase-II trial, involving 10 patients with hepatocellular cancer (HCC) as a model disease, we attempted to (1) study short-term changes in serum biomarkers following treatment with octreotide (targeting VEGF) alone or octreotide added by imatinib (400 mg/d, additionally targeting PDGF); (2) to explore a potentially decreased metabolisation of imatinib because of hepatic impairment; and (3) to correlate pharmakokinetic and pharmacodynamic findings (PK/PD modelling). Results: Compared to literature results, PK parameters for imatinib are similiar to patients with normal liver function, however, the main active metabolite N-DMI shows a more prolonged half-life. The AUC of N-DMI depends on liver function as expressed by CPT score (r= −0.67) and serum bilirubine (r= −0.70), p<0.05 each. During short-termed imatinib treatment (4 weeks), plasma PDGF significantly decreased at week 2 compared to controls only receiving octreotide treatment. VEGF secretion was unaffected by imatinib. The AUC of N-DMI could be attributed to the pharmacodynamic effect of PDGF inhibition (r= −0,679 [−0.917 to −0.0868], p = 0.031). Conclusions: In HCC patients with different stages of liver cirrhosis, the metabolisation of N-DMI, but not imatinib, is impaired. PK of imatinib is closely correlated to PDGF inhibition. Whether this translates into antiangiogenesis and tumor regression must be awaited by long term clinical studies.

[Table: see text]

No significant financial relationships to disclose.

Prevalence and spread of enterohepatic Helicobacter species in mice reared in a specific-pathogen-free animal facility

Infections with enterohepatic Helicobacter species (EHS) can change the results of animal experiments. However, there is little information about the prevalence of EHS in noncommercial animal facilities. The aim of this study was to investigate the prevalence and the spread of EHS in specific-pathogen-free (SPF) mice. Fecal samples of 40 mouse lines were analyzed for members of the family Helicobacteraceae using a group-specific PCR targeting the 16S rRNA gene. Additional experiments were carried out to evaluate the spread of EHS among mice harbored in different caging systems. Helicobacter species were detected in 87.5% of the mouse lines tested. Five different Helicobacter species were identified: H. ganmani, H. hepaticus, H. typhlonicus, and the putative Helicobacter species represented by the isolates hamster B and MIT 98-5357. Helicobacter infection did not spread between animals in neighboring cages when individually ventilated cages were used; in contrast, when the mice were reared in open-air cages, EHS were found to spread from cage to cage. However, the spread was prevented by adding polycarbonate filter tops to the cages. When Helicobacter-negative and infected mice shared the same cage, transmission of the infection occurred in 100% within 2 weeks. Furthermore, we found that mice from commercial breeding facilities may carry undetected Helicobacter infections. Taken together, we show that infection with EHS may frequently occur and spread easily in mice reared under SPF conditions despite extensive safety precautions. Moreover, there is a high prevalence of rather uncommon Helicobacter species that may be a consequence of the current routine procedures used for health screening of SPF mice.

Effects of low-dose aspirin on gastric erosions, cyclooxygenase expression and mucosal prostaglandin-E2 do not depend on Helicobacter pylori infection

BACKGROUND

The mechanisms by which Helicobacter pylori and low-dose aspirin induce gastric damage are not completely elucidated.

AIM

To evaluate the effects of low-dose aspirin on gastric damage, mucosal prostaglandin-E(2) levels and cyclooxygenase-enzyme expression in relation to the H. pylori status.

METHODS

Twenty healthy volunteers (H. pylori positive, n = 10; H. pylori negative, n = 10) received aspirin 100 mg/die for 1 week. At days 0, 1, 3 and 7, gastric mucosal lesions were studied by oesophagogastroduodenoscopy and histology. COX-1 and COX-2 were determined by immunohistochemistry and reverse-transcriptase polymerase chain reaction, and mucosal prostaglandin-E(2) levels by enzyme-linked immunosorbent assay. Nine H. pylori-positive subjects repeated the protocol after H. pylori eradication.

RESULTS

All groups developed a similar number of erosions. COX-1 and COX-2 expression, as well as mucosal prostaglandin-E(2) levels were not influenced by H. pylori status and aspirin medication. Helicobacter pylori-negative and H. pylori-eradicated subjects who developed aspirin-induced erosions had significant lower pre-treatment antral prostaglandin-E(2) levels than those without erosions (3.6 ng/microg vs. 6.3 ng/microg protein and 3.6 ng/microg vs. 6.0 ng/microg protein, respectively, P < 0.01 Mann-Whitney U-test).

CONCLUSIONS

In healthy subjects, low-dose aspirin for 1 week does neither affect cyclooxygenase expression nor mucosal prostaglandin-E(2) levels. Antral prostaglandin-E(2)-basal levels appear to be critical for development of aspirin-induced gastric damage in subjects without H. pylori infection.

The effect of single-dose naproxen on eicosanoid formation in human gastroduodenal mucosa

BACKGROUND

In animal studies, aspirin and non-aspirin non-steroidal anti-inflammatory drugs contribute to gastroduodenal damage via cyclo-oxygenase inhibition and consecutive leucotriene formation (COX-LOX eicosanoid shunt).

AIM AND METHODS

Ten Helicobacter pylori-negative healthy volunteers received a single dose of 500 mg naproxen to address two questions: (i) is there a crosstalk between eicosanoids before medication in the human gastroduodenal mucosa and (ii) can we demonstrate a COX-LOX shunt following single-dose naproxen?

RESULTS

Significant correlations in the stomach mucosa before medication were obtained between leucotriene B4 (LTB4) and thromboxane B(2) (TxB(2); r = -0.38, P = 0.05), as well as LTB4 and prostaglandin E(2) (PGE(2); r = 0.71, P < 0.0001). In serum, a >90% inhibition of TxB(2) and PGE(2) occurred within 30 min of naproxen administration. In gastric mucosa, a significant decrease of TxB(2) occurred already at 15 min and preferably in the antrum. For LTB4 there was a non-significant trend towards a transient increase. Mucosal PGE(2) was unchanged in all regions; transcript levels of both cyclo-oxygenases/5-lipoxygenase were unaffected (except for a trend of increasing cyclo-oxygenase-2 in the corpus).

CONCLUSIONS

Baseline correlations between LTB4-TxB(2) and LTB4-PGE(2) reflect a crosstalk between these eicosanoids. A COX-LOX shunt; however, cannot be demonstrated following single-dose naproxen in a low-risk population.

Simultaneous detection and differentiation of anti-Helicobacter pylori antibodies by flow microparticle immunofluorescence assay

Helicobacter pylori is the key pathogen for gastroduodenal diseases. The clinical outcome of H. pylori infection is influenced by the presence of strain-specific virulence factors that are usually detected by the presence of specific anti-H. pylori antibodies in serum. Apart from the detection of these antibodies by enzyme-linked immunosorbent assay (ELISA), it is desirable to obtain additional information concerning the presence of certain virulence factors of H. pylori that are currently detected by immunoblot analysis. At present, the immunodiagnosis of an H. pylori infection includes two separate methods: ELISA and immunoblot analysis. Here, we report the development and evaluation of a new rapid flow microparticle immunofluorescence assay (FMIA) for detection of anti-H. pylori antibodies in human serum. The assay allows rapid qualitative and quantitative detection of anti-H. pylori antibodies by using crude antigen preparations as well as single recombinant antigens (urease A, urease B, CagA, and alkylhydroxy peroxide reductase) in the same sample with one measurement, and thus it combines the advantages of enzyme immunoassay and Western blot analysis. Seventy-five patient samples were analyzed by FMIA, ELISA, and Western blotting with respect to their immunoreactivity against crude H. pylori extracts and individual H. pylori antigens. Statistical analyses revealed an overall similarity of more than 90% among the results for FMIA, ELISA, and Western blot. Therefore, we conclude that FMIA is a powerful and time- and cost-saving assay system for the detection of antimicrobial antibodies, with higher sensitivity and a larger measurement range than ELISA.

Anti-CagA and anti-VacA antibodies in Helicobacter pylori-infected patients with and without peptic ulcer disease in Serbia and Montenegro

BACKGROUND

The expression of two Helicobacter pylori proteins, CagA and VacA, is associated with more severe pathogenesis and clinical outcomes of the infection. However, this association varies among geographical regions and ethnic groups. We therefore evaluated CagA and VacA seroprevalence in H. pylori-positive dyspeptic patients in Serbia and Montenegro.

METHODS

In 173 consecutive dyspeptic patients referred to endoscopy (67M, mean age 49 +/- 15, 76 smokers), immunoblot assay was used to detect serum antibodies against CagA and VacA. Presence of H. pylori infection was assessed using a rapid urease test (RUT), routine histology and serology (anti-IgG ELISA). Duodenal ulcer (DU) was diagnosed in 28, gastric ulcer (GU) in 3 and non-ulcer dyspepsia (NUD) in the remaining 142 patients.

RESULTS

129 (74.6%) patients were H. pylori-positive, 27 (96.4%) with DU, 3 (100%) with GU and 99 (69.7%) with NUD (P < 0.01); 121 (93.8%) patients carried anti-CagA antibodies and there was no difference between the DU and NUD groups. VacA antibodies were detected in sera of 50 (38.75%) and were more prevalent in patients with DU compared to the NUD group (P < 0.05).

CONCLUSIONS

In Serbia and Montenegro there is high seroprevalence of CagA-positive H. pylori strains in dyspeptic patients with and without peptic ulcer, while VacA-positive strains are more closely related to peptic ulcer disease.

Diagnostics of Helicobacter pylori Infection in Patients with Peptic Ulcer Bleeding

BACKGROUND

In peptic ulcer bleeding, the sensitivity of H. pylori tests, in particular of the rapid urease test (RUT), has been reported to be insufficient.

AIM

To validate the RUT, serology and the urea breath test were carried out in patients with bleeding peptic ulcers, and to study the influence of H. pylori suppressive treatment (HpSuT), i. e., antibiotics and proton pump inhibitors.

PATIENTS AND METHODS

123 consecutive patients (mean age 65.5 years) with a relevant bleeding from gastric or duodenal ulcers were prospectively tested for H. pylori infection by directs tests (RUT, histology, culture, urea breath test) and by IgG serology as an indirect test. Positive H. pylori status was defined by positive histology or culture.

RESULTS

In patients without HpSuT during the preceding four weeks (N = 83), the sensitivity and specificity of RUT was 94 and 84 %, that of serology 83 and 68 % respectively. The sensitivity of urea breath test decreased from 82 to 60 % after even one day of HpSuT. In the overall group, the duration of HpSuT and preceding hospitalization were independent factors linked with negative results of all direct tests.

CONCLUSIONS

In peptic ulcer bleeding, RUT combined with histology is an adequate diagnostic approach. However, false negative results have to be considered following even short-term HpSuT or hospitalization. Non-invasive diagnosis based on serology alone is inaccurate and should be complemented by the urea breath test prior to starting HpSuT.

Antigen stool test for assessment of Helicobacter pylori infection in patients with upper gastrointestinal bleeding

BACKGROUND

Re-bleeding of Helicobacter pylori-associated peptic ulcer disease is reduced by H. pylori eradication.

AIM

To validate a non-invasive test, the Premium Platinum HpSA stool test, in patients with upper gastrointestinal bleeding.

METHODS

Stool samples of consecutive patients with relevant bleeding from gastric or duodenal ulcers or erosions were collected at initial endoscopy and during the following week. Samples were assessed using the HpSA test. H. pylori status was defined by three biopsy-based reference methods: culture, rapid urease test and histology. It was positive if culture was positive or if rapid urease test and histology were positive.

RESULTS

One hundred and fourteen patients (mean age, 66 years) were included. In accordance with the definition, 56 (49%) were H. pylori positive. The sensitivity and specificity of the first stool sample were 84% and 90%, respectively. The respective values for two samples from consecutive days were 91% and 86%. In comparison with a serum immunoglobulin G antibody enzyme-linked immunoabsorbent assay, the HpSA test showed superior specificity.

CONCLUSIONS

The diagnostic accuracy, in particular the sensitivity, of the HpSA stool test is reduced by upper gastrointestinal bleeding. The positive predictive value of 89%, however, justifies the initiation of eradication therapy on the basis of a positive stool test. A negative test result should be confirmed by a further diagnostic method.

Comparative evaluation of two hemagglutination tests for the detection of anti-Helicobacter pylori antibodies

Two hemagglutination assays (IHAs) for detecting anti-H. pylori antibodies were evaluated. In 257 patients, both tests revealed sensitivity or specificity values between 71-79% or 81-82%, respectively, which were lower than those of an anti-H. pylori ELISA. Notably, the sensitivities of both IHAs varied in subgroups of patients between 48-95%. Based on the validation, the IgG-ELISA is superior to both IHAs tested, and therefore, should be used in routine diagnostics.

Human cathepsin W, a cysteine protease predominantly expressed in NK cells, is mainly localized in the endoplasmic reticulum

Human cathepsin W (also called lymphopain) is a recently described papain-like cysteine protease of unknown function whose gene expression was found to be restricted to cytotoxic cells. Here we demonstrate that cathepsin W is expressed predominantly in NK cells and, to a lesser extent, in CTLs. Quantitative RT-PCR revealed that NK cells contained approximately 21 times more cathepsin W transcript than CTLs. The predominant expression of cathepsin W in NK cells was further confirmed by Western blot analysis and immunohistochemistry. IL-2-mediated stimulation of NK cells and CTLs revealed a stronger up-regulation of the cathepsin W gene and protein expression in NK cells (7-fold) than in CTLs (2-fold). Transfection experiments of HeLa cells and biochemical analyses revealed that cathepsin W is exclusively "high mannose-type" glycosylated and is mainly targeted to the endoplasmic reticulum (ER). Interestingly, the ER localization of cathepsin W was also found in NK cells, in which colocalization studies revealed an overlapping staining of cathepsin W and Con A, an ER-specific lectin. Furthermore, subcellular fractionation of cathepsin W-expressing cells confirmed the ER localization and showed that cathepsin W is membrane associated. Based on the results of this study, cathepsin W might represent a putative component of the ER-resident proteolytic machinery. The constitutive expression in NK cells and the stronger up-regulation of cathepsin W by IL-2 in NK cells than CTLs suggest that cathepsin W is not just a marker of cytotoxic cells but is, rather, specifically expressed in NK cells.

TIN-ag-RP, a novel catalytically inactive cathepsin B-related protein with EGF domains, is predominantly expressed in vascular smooth muscle cells

A human cDNA of 2166 bp encoding a novel cathepsin B-related protein was isolated and characterized. The amino acid sequence of the predicted protein of 467 aa was 46% identical with that of human tubulointerstitial nephritis antigen (TIN-ag), and therefore, the protein was tentatively designated as the TIN-ag-related protein (TIN-ag-RP). The amino acid sequence of TIN-ag-RP is composed of a 21 aa long signal sequence, a 181 aa long N-terminal domain containing two epidermal growth factor-like domains, a follistatin motif, and a 265 aa long cathepsin B-like domain. Interestingly, a serine residue has replaced the active site cysteine residue in the cathepsin B-like domain, resulting in a proteolytically inactive protein. Evolutionary analysis revealed that a distinct family of "TIN-ag-like" proteins had evolved in vertebrates. Northern blot analysis revealed a single TIN-ag-RP transcript of 2.4 kb in various tissues with the highest transcript levels detected in aorta, heart, placenta, skeletal muscle, kidney, and a colorectal adenocarcinoma cell line. Using a polyclonal anti-TIN-ag-RP antibody, TIN-ag-RP expression was predominantly seen in vascular smooth muscle (VSM) cells, but also in cardiac and skeletal muscle cells as well as in kidney. Interestingly, uterine smooth muscle cells completely lacked TIN-ag-RP expression, implying a regulated gene expression. Localization studies in HeLa cells stably transfected with TIN-ag-RP cDNA showed that TIN-ag-RP is glycosylated and actively secreted, a finding in line with its proposed function as a structural or regulatory protein similar to TIN-ag.

Cloning, characterization, and expression of the human TIN-ag-RP gene encoding a novel putative extracellular matrix protein

The human gene encoding a novel tubulointerstitial nephritis antigen (TIN-ag)-related protein (TIN-ag-RP) was isolated, and its genomic organization was determined. BLAST searches revealed the highest degree of homology to several mammalian TIN-ag orthologues, and a weak homology to cathepsin B-like proteases. The 12 kb gene was mapped by fluorescence in situ hybridization to chromosome 1p34.2-3, a locus neither related to that of the human TIN-ag (6p11.2-12) nor to that of cathepsin B (8p22-23.1). The TIN-ag-RP is encoded in ten exons with introns ranging from 83 bp to 4 kb. In addition, the gene contained one exon in the 5'UTR, but none in the 3'UTR. Five of the 10 splice sites of the TIN-ag-RP gene were fully conserved when compared to a related gene of C. elegans, whereas only one splice site was identical to those found in cathepsin B genes. Furthermore, human TIN-ag-RP tagged with the T7-epitope, was expressed in HeLa cells, and was found to be localized in vesicular compartments as well as secreted into the medium suggesting the involvement of the endosomal trafficking pathway. Based on the high degree of homology of the amino acid sequences and genomic organization between TIN-ag-RP and TIN-ag, we suggest that both molecules may form a distinct group or family of TIN-ag-like proteins.

The human cathepsin F gene--a fusion product between an ancestral cathepsin and cystatin gene

Human cathepsin F is a novel papain-like cysteine protease of unknown function. Here, we describe the complete human cathepsin F (CTSF) gene which is composed of 13 exons. In addition to a previous report, two novel upstream located exons whose splice sites interrupted the propeptide of cathepsin F within the 'cystatin-like' domain, recently described by Nagler et al. (Biochem. Biophys. Res. Comm. 257, 313-318, 1999) were identified. A comparison of the genomic structures between this novel part of the cathepsin F gene and those of several cystatin genes revealed striking similarities, supporting the hypothesis that the cathepsin F gene resulted from a gene fusion between an ancestral cystatin and cathepsin gene.

Role of alanyl aminopeptidase in growth and function of human T cells (review)

Alanyl aminopeptidase (APN, CD13) is highly expressed in human monocytes, and anti-CD13 monoclonal antibodies are well established routine markers in leukaemia typing. Due to activation or malignant transformation other leukocyte subpopulations including human T cells exhibit significant APN-gene and surface expression. The function of leukocyte APN is poorly understood, especially the knowledge of physiological ligands/substrates of the enzyme is limited. Abnormal expression of APN on malignant lymphocytes, the activation-dependent induction of APN expression in peripheral T cells and the strong anti-proliferative effects of aminopeptidase inhibitors lead to the interesting hypothesis of a linkage of APN expression and/or function to leukocyte growth. In support of this hypothesis we detected mutations in the APN-gene of patients suffering from leukaemia or lymphoma. This review outlines evidence for APN contributing to the regulation and realisation of lymphocyte growth and function by modulating the mRNA expression of IL-2, IL-1 receptor antagonist, and TGF-beta1 and increasing the activity of MAP kinase p42/Erk2.

Human cathepsins F and W: A new subgroup of cathepsins

Human cathepsin F is a recently described papain-like cysteine protease of unknown function. To investigate the evolutionary relatedness to other human cathepsins, we determined the genomic organization and the chromosomal localization of cathepsin F and isolated its putative promoter region. The gene of human cathepsin F (CTSF) is composed of twelve exons and eleven introns and was found to be similar to that of cathepsin W but different from the cathepsins K, S, L, O, B, and C. The splice sites of nine out of the eleven introns were identical to those determined in the cathepsin W gene (CTSW), whereas introns one and ten were unique for CTSF. The 4. 7 kb gene was mapped to the long arm of chromosome 11 at position q13.1-3, a locus shared with CTSW. Phylogenetic analysis of human cathepsin protein sequences demonstrated that (i) cathepsins F and W are evolutionarily separated from other human cathepsins, and (ii) cysteine proteases closely related to human cathepsin W and F are also expressed in parasites and mammals. Based on these phylogenetic findings, on the presence of a particular protein motif ("ERFNAQ") in the propeptides of cathepsins F and W as well as the genomic organization and chromosomal localization of their genes, we concluded that F and W form a novel subgroup of cathepsin proteases. We suggest the naming "cathepsin F-like" proteases distinct from the previously described cathepsins "L- and B-like" subgroups.

Clinicopathologic implications of MDM2, p53 and K-ras gene alterations in osteosarcomas: MDM2 amplification and p53 mutations found in progressive tumors

It is widely recognized that various oncogenes and tumor suppressor genes contribute to tumorigenesis and progression of osteosarcomas. However, whether genetic alternations enable us to predict the prognosis of patients with osteosarcomas is unclear. Southern blotting and polymerase chain reaction/single strand conformation polymorphism (PCR-SSCP) analyses were performed to search for MDM2, ras family and p53 gene alterations in 17 patients with high-grade osteosarcomas. Amplification of the MDM2 gene was found in three tumors, two of which were obtained from a regional lymph node metastasis and the other from a locally advanced lesion. Point mutations of the p53 gene were found in exons 4 and 5 in two tumors each. One of the four tumors with p53 mutations was obtained from a lymph node metastasis, one from a recurrent tumor and another from the primary tumor of a patient who developed lung metastases. Coexistence of MDM2 amplification with point mutation of the p53 gene was observed in two tumors. A point mutation of the K-ras oncogene was detected at codon 13 in two tumors. MDM2 amplification and p53 mutation may reflect tumor progression, although no correlation between alteration and response to chemotherapy or patient survival was demonstrated.

Genomic structure, chromosomal localization, and expression of human cathepsin W

A 12 kb genomic fragment containing the entire open reading frame of the human cathepsin W was isolated and the genomic organization of this papain-like protease gene was determined. The 3.8 kb gene was mapped by fluorescence in situ hybridization to chromosome 11q13.1. The gene contained ten exons with introns ranging from 81 to 1119 bp. Four of the nine introns and a 5' untranslated exon were conserved when compared to related genes such as cathepsins L, K and S, whereas there was no similarity to the genomic organization of cathepsins B or C. In contrast to conserved splice site locations in other cysteine protease family members, the cathepsin W gene contained five unique locations. Furthermore, human cathepsin W cDNA was expressed, and was found to be localized within the rough endoplasmic reticulum in transiently transfected Cos-7 and Hela cells.

The activation-dependent induction of APN-(CD13) in T-cells is controlled at different levels of gene expression

Recently, it was shown that aminopeptidase N (E.C. 3.4.11.2, CD13) is up-regulated during mitogenic stimulation of peripheral T-cells. In this study, we demonstrate that the half-life of APN mRNA was considerably prolonged in these cells leading to a 2.7-fold increase of APN transcript level. The apparent half-life time of the APN transcript was investigated by the RNA synthesis inhibitor-chase method using actinomycin D. The steady-state APN mRNA levels was determined by a competitive RT-PCR. The half-lives estimated in resting T-cells, natural killer cells and permanently growing tumour cells varied between 3.5 and 6 h. Finally, nuclear run-on assays revealed that the APN gene expression of stimulated T-cells is controlled by increased promoter activity as well. These studies suggest a control of APN gene expression at the post-transcriptional level in addition to promoter-mediated regulation.

Rapid mitogen-induced aminopeptidase N surface expression in human T cells is dominated by mechanisms independent of de novo protein biosynthesis

The membrane bound metalloprotease aminopeptidase N (APN, CD13, EC 3.4.11.2) is a well established marker of normal and malignant cells of the myelo-monocytic lineage. It is also expressed by leukaemic blasts of a small group of patients suffering from acute or chronic lymphoid leukaemia. Recently, the expression of the APN gene in T cell lines as well as the induction of APN gene and surface expression in human peripheral T cells by mitogenic activation have been demonstrated. Here, by means of cytofluorimetric analysis evidence is provided, that the induction of APN surface expression is partially resistent to the action of the inhibitors of protein biosynthesis, puromycin and cycloheximide, and is not prevented by tunicamycin, an inhibitor of glycosylation. These data suggest that the rapid mitogen-induced surface expression of APN, detectable 20 hours after stimulation is dominated by mechanisms not dependent on de novo protein biosynthesis or glycosylation. As shown by simultaneous analyses, the inhibitors used did also differently modify the induction of surface expression of other inducible glycosylated leukocyte surface antigens, namely CD25, CD69 and CD95.

The main neutral aminopeptidase activity of human lymphoid tumour cell lines does not originate from the aminopeptidase N-(APN; CD13) gene

Lymphocytes and related cell lines are predominantly CD13-negative, however, there are reports describing neutral aminopeptidase activity in or on these cells. The aim of this study was to answer the question, whether this activity originates from APN-gene expression. The total cellular activities (Ala-pNA hydrolysis) of lymphoid cell lines are up to 15 times higher than that of normal lymphocytes. Despite weak or lacking CD13 surface expression all lymphoid cell lines tested contain APNmRNA as quantified by competitive RT-PCR as well as low enzymatic activity in their particulate fractions. By isoelectric focusing two enzyme species with isoelectric points of 5.4 or between 3.5 to 4.8, respectively, were detected. To investigate whether these activities result from APN-gene we established transfectants lacking cellular APN expression of the CD13-positive histiocytic cell line U937 and the CD13-negative T-cell line H9. Studies on these transfectants proved (I) that the main neutral aminopeptidase activity expressed in lymphoid cells is definitively not related to APN and (II) that APN is also expressed in lymphoid cells, although on a low level only.

Induction of the membrane alanyl aminopeptidase gene and surface expression in human T-cells by mitogenic activation

The metal-dependent membrane alanyl aminopeptidase (amino-peptidase N, APN, CD13; EC 3.4.11.2) is a well-established marker of normal and malignant cells of the myelo-monocytic lineage. It is also expressed by leukaemic blasts of a small group of patients suffering from acute or chronic lymphoid leukaemia. CD13-specific monoclonal antibodies do not bind to the surface of normal B lymphocytes, and APN mRNA was not detectable by Northern analysis in normal lymphocytes or in T-cell lines. Recently the expression of the APN gene in T-cell lines as well as the ability of these cells to cleave chromogenic substrates preferred by APN have been demonstrated [Lendeckel, Wex, Kähne, Frank, Reinhold and Ansorge (1994) Cell. Immunol. 153, 214-226]. Here, by means of dot-blot hybridization and RNase protection assay, evidence is provided that human peripheral T-cells as well as derived cell lines contain significant amounts of APN mRNA, comparable to that in the promyeloic cell line U937, and that mitogenic activation of peripheral human T-cells leads to a more than 4-fold increase in their APN mRNA content. In the course of activation, T-cells increase their total alanine p-nitroanilide-hydrolysing activity to approx. 7-fold that of resting cells. Furthermore these cells become immunoreactive towards CD13 to a significant extent (up to 51%) as shown by surface staining and confirmed by activity staining and immunostaining after isoelectric focusing (pI of T-cell APN = 4.6). In addition it is demonstrated by fluorescence microscopy that viable, activated T-cells effectively cleave the fluorogenic aminopeptidase substrate bis-glycyl-rhodamine 110 and that the corresponding aminopeptidase activity is associated with the cell surface. We show that specific inhibitors of APN, probestin and actinonin, strongly decrease DNA synthesis in phytohaemagglutinin (PHA)-stimulated T-cells. In summary, evidence is presented that in the course of mitogenic activation human peripheral T-cells increase the expression of APN both at the transcriptional level and at the cell surface. This has been demonstrated both at the APN mRNA level and at the protein level with respect to aminopeptidase enzymic activity and CD13 immunoreactivity.

Quantification of aminopeptidase N mRNA in T cells by competitive PCR

The aminopeptidase N (CD13, EC 3.4.11.2) is a well-characterized surface molecule expressed in a variety of cell types and species. Recent data indicate an expression of the APN mRNA and the corresponding aminopeptidase activity in human peripheral T cells and related cell lines as well. Here, the sensitive method of competitive PCR was used to quantify low amounts of APN mRNA in T cell lines. An APN cDNA fragment enshortened by a deletion of 87 bp was used as an internal APN-specific standard. The myelo-monocytic cell line U937 and the lymphoid T cell lines HuT78 and H9 contain 2.3 x 10(7), 5.9 x 10(6) and 5.6 x 10(6) copies/micrograms total RNA, corresponding to 160, 70 and 50 copies/cell, respectively. These data have been confirmed by determination of the APN activity, that represents a fraction only of the total cellular neutral aminopeptidase activity in hematopoetic cells. In the case of the CD13-positive cell line U937, approximately 60-70% of the total neutral aminopeptidase activity could be attributed to APN. In contrast, only a minor fraction (5-20%) of the cellular neutral aminopeptidase activity in the T cell lines H9 and HuT78 represents APN. The results suggest that APN gene expression within the hematopoetic system is not restricted to myelo-monocytic cells, instead a low APN expression may be a common feature of lymphocytes, at least of T cells, too.

Expression of the aminopeptidase N (CD13) gene in the human T cell lines HuT78 and H9

The membrane-bound metalloprotease aminopeptidase N (APN, CD13, EC 3.4.11.2) is a well-established marker of normal and malignant cells of the myelomonocytic lineages. It is also expressed by leukemic blasts of a small group of patients suffering from acute or chronic lymphoid leukemia. CD13-specific monoclonal antibodies do not bind to the surface of normal B lymphocytes and APN-mRNA was not detectable by Northern analysis in normal lymphocytes or in T cell lines. A recent paper, however, describes the expression of CD13 on concanavalin A-stimulated T cells. Here, by means of enzymatic amplification of cDNA, cloning and sequencing of amplified cDNA fragments, in situ hybridization, and transcription start site mapping, evidence is provided that the human T cell lines HuT78 and H9 do contain APN-mRNA. Ala-pNA-hydrolyzing activity was detected in viable cells and cell homogenates as well as in size-fractionated protein fractions. Alanine-beta-naphthylamide (Ala-beta NA)-hydrolyzing activity was readily detectable after isoelectric focusing and blotting and was shown to be localized exclusively intracellularly in both cell lines. Usage of aminopeptidase-specific effectors revealed this activity to be distinct from CD13.